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1. What are the Objectives of a Successful Abandonment?2. What Materials & Techniques are Used?3. What do the Regulations Require?4. What Special Challenges Exist Offshore?5. What makes Subsea Well Abandonment Unique?6. What is Rigless P&A?7. What is Sustained Casing Pressure?8. Why do Some Wells Require Reabandonment?9. What New Technologies are Available?10. What Best Practices Ensure a Successful Offshore P&A?
Prevent Migration of Fluids within the Wellbore◦ Isolate Hydrocarbon Zones◦ Protect Fresh Water AquifersPrevent Release of Formation Fluids to the EnvironmentRestore Surface Uses◦ Remove Wellhead / Xmas Tree◦ Cut Casings Below Ground Level / Sea FloorMeet Regulatory RequirementsMinimize Environmental Impacts during Operations◦ Maintain Well Control◦ Avoid Spills◦ Minimize Environmental Effects (Air Emissions, Biological Impacts)
Insert Well Diagram
1. Seal Fluid Pathways Created to Produce Oil & Gas◦ Perforations◦ Slotted Liners
2. Remedy Deficiencies / Failures in Well Construction◦ Cement Channels◦ Lack of Cement◦ Casing Leaks
Materials Used to Seal Fluid PathwaysCommon◦ Cement: Used since 1920s±◦ Mechanical Seals: e.g., Bridge Plug -
cast iron, steel, elastomers
Other◦ Bentonite Pellets ◦ Epoxies, Resins, Polymers
Historical◦ Wooden Plugs
Abandonment TechniquesCement Placement Techniques◦ Balanced Plug◦ Squeezing – Pumping cement
under pressure
Severing Techniques◦ Explosives◦ Mechanical Cutter◦ Abrasive Jetting◦ Bandsaw◦ Diamond Wire◦ Torch Cutting
DOGGR: Onshore, Offshore State Waters
CSLC: Offshore State Waters
MMS: Offshore Federal Waters
Other Federal, State & Local Agencies may be involved depending on project scope.
Equipment Availability◦ Lack of mobile rigs on west coastOperating Challenges◦ Weather◦ Seas◦ Logistics◦ CorrosionMore Elaborate Well Completions◦ Multiple Tubing strings ◦ Chemical Injection Lines/ Sensor CablesStricter Environmental RequirementsSubsea Wells
Wellhead Equipment is Located on Sea Floor◦ Rather than above sea level
(e.g., on platform or island)◦
Wellhead/Tree Design◦ Obsolete / One-Off Designs◦ Well Control Equip./Procedures◦ Complicated Flowpaths◦ Custom Tool Fabrication
Special Resources Required◦ Divers◦ Mobile Drilling Rig or Rigless
Abandonment operations conducted without a conventional drilling or workover rig, using• Coiled Tubing, Wireline, Pumps,
Crane, and/or Workboat/Barge
Hydraulic Workover Units (snubbing units) offer similar benefits & can overcome certain rigless limitations
Benefits+ Avoid rig mobilization+ Generally lower cost+ Avoid tubular disposal+ Often lower well control risk
Limitations- Inability to fish stuck tubing/
tools- Casing recovery difficult- Difficult w/ some completions
aka: Annular Gas Pressure, Casing Vent Flow
Sustained pressure on the annuli of production or surface casing.
Cause: Presence of a flow path to the surface from higher pressure subsurface zones
• Uncemented annulus
• Channel through a cemented annulusCan develop during well constructionCan develop over time
SolutionsDiagnosis Source◦ Research◦ Fluid analysis◦ Logging
Remediation◦ Cement squeezing
From surface, orThru perforations
◦ Cement plugAfter casing removal
◦ Cement CirculationThrough cut or perfs
1. Leak DevelopsOriginal Abandonment Fails or Was Never PerformedChanging subsurface conditions
• E.g., Repressurization, earth movement
Temporary P&A (e.g., wellhead not removed), Uncemented AnnulusInadequate well constructionHistorical P&A Practices –e.g., wooden plugs
2. Original P&A Doesn’t Meet Current Requirements
Rebandonment is called for when land development or construction will prevent future access to the well.
3. The Well becomes ExposedSubsidenceStorm / Tidal ActionDevelopment / Grading / Dredging
Cement Plug Placement Tools
Specialty Cements
Low Melting-Point Metal Alloys
Rigless Integrated Tools (Annular perforation and circulation)
PlanningThorough Understanding of Subsurface Conditions
Original Well ConstructionCurrent Wellbore, Reservoir & Geologic ConditionsField Practices – lift methods, historical problems
Evaluation of Surface ConditionsWellhead /Tree ConditionEquipment / Material LogisticsMarine ConditionsImpact Mitigation
Detailed Abandonment PlanAbandonment DesignCement DesignContingency PlanningWell Control PlanningHealth, Environment & Safety Planning
ExecutionAbility to Respond to ChangesLab Testing of Cement SlurriesWellbore CleaningEffective Cement Placement Minimize Cement Contamination